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1 .Listen to part of a lecture in an astronomy class.
2 .You will not need to remember the numbers the professor mentions.
1 .OK. Let's get going.
2 .Today I'm going to talk about how the asteroid belt was discovered.
3 .And... I'm going to start by writing some numbers on the board.
4 .Here they are; We'll start with zero, then 3, ... 6, ... 12.
5 .Uh, tell me what I'm doing.
1 .Multiplying by 2?
2 .Right, I'm doubling the numbers, so 2 times 12 is 24, and the next one I'm going to write after 24 would be...
不错。我在使这些数翻倍，所以2 乘以12 是24，24 之后我要写的数是……
1 .48. Then 96.
2 .We'll stop there for now.
3 .Uh, now I'll write another row of numbers under that.
4 .Tell me what I'm doing.
5 .4, 7, 10... How am I getting the second row?
1 .Adding 4 to the numbers in the first row.
1 .I'm adding 4 to each number in the first row to give you a second row.
2 .So the last two will be 52, 100, and now tell me what I'm doing.
1 .Putting in a decimal?
1 .Yes, I divided all those numbers by 10 by putting in a decimal point.
2 .Now I'm going to write the names of the planets under the numbers.
3 .Mercury... Venus... Earth... Mars.
4 .So, what do the numbers mean?
5 .Do you remember from the reading?
1 .Is it the distance of the planets from the Sun?
1 .Right. In astronomical units - not perfect, but tantalizingly close.
2 .The value for Mars is off by... 6 or 7 percent or so.
3 .It's... but it's within 10 percent of the average distance to Mars from the Sun.
4 .But I kind of have to skip the one after Mars for now.
5 .Then Jupiter's right there at 5-point something, and then Saturn is about 10 astronomical units from the Sun.
然后这边的木星到太阳有5 个左右天文单位的距离，之后土星到太阳的距离大概有10 个天文单位。
6 .Um, well, this pattern is known as Bode's Law.
1 .Um, it isn't really a scientific law, not in the sense of predicting gravitation mathematically or something, but it's attempting a pattern in the spacing of the planets, and it was noticed by Bode hundreds of years ago.
2 .Well, you can imagine that there was some interest in why the 2.8 spot in the pattern was skipped, and um... but there wasn't anything obvious there, in the early telescopes.
3 .Then what happened in the late 1700s?
4 .The discovery of...?
1 .Another planet?
1 .The next planet out, Uranus - after Saturn.
1 .And look, Uranus fits in the next spot in the pattern pretty nicely, um, not perfectly, but close.
2 .And so then people got really excited about the validity of this thing and finding the missing object between Mars and Jupiter.
3 .And telescopes, remember, were getting better.
4 .So people went to work on finding objects that would be at that missing distance from the Sun, and then in 1801, the object Ceres was discovered.
1 .And Ceres was in the right place - the missing spot.
2 .Uh, but it was way too faint to be a planet.
3 .It looked like a little star.
4 .Uh, and because of its star-like appearance, um, it was called an "asteroid".
5 .OK? "Aster" is Greek for "star", as in "astronomy".
6 .Um, and so, Ceres was the first and is the largest of what became many objects discovered at that same distance.
7 .Not just one thing, but all the objects found at that distance form the asteroid belt.
8 .So the asteroid belt is the most famous success of this Bode's Law.
9 .That's how the asteroid belt was discovered.